neural regulation in animals

• Action potential


  • Depolarization of the membrane potential to a positive value
  • Followed by repolarization back to the resting potential
• Threshold


  • Minimum level of stimulus required to trigger an action potential
• Resting potential


  • Negative membrane potential when the cell is at rest
• Action potential generation


  1. Sodium channel opens

  2. Sodium rushes in

  3. Membrane depolarizes

  4. Potassium channel opens

  5. Potassium rushes out

  6. Membrane repolarizes
• Blood pressure/volume regulation


  1. Sensors in JGA detect decrease

  2. JGA releases renin

  3. Renin converts angiotensinogen to angiotensin I

  4. ACE converts angiotensin I to angiotensin II

  5. Angiotensin II causes arterioles to constrict

  6. Aldosterone causes Na+ and H2O reabsorption
• Concepts covered in today's lesson

  • Central and peripheral nervous system
  • Sensing a stimulus
  • Hearing
  • Vision
  • Taste & smell
  • Muscle action
• Central Nervous System (CNS)


  Information processing center
• Peripheral Nervous System (PNS)


  Transmits information to/from CNS, regulates movement and internal environment
• PNS components


  • Afferent neurons
  • Efferent neurons
• Efferent divisions


  • Motor system
  • Autonomic nervous system
• Autonomic nervous system divisions


  • Sympathetic
  • Parasympathetic
  • Enteric
• Sensory reception


  Detection of stimuli by sensory receptors
• Transduction


  Converting energy into a change in membrane potential of sensory receptors
• Transmission


  Sending signals to the central nervous system
• Integration


  Processing of sensory information
• Perceptions are the brain's construction of stimuli
• Amplification


  Strengthening of a sensory signal during transduction
• Sensory adaptation


  Decrease in responsiveness to continued stimulation
• Types of sensory receptors

  • Mechanoreceptors
  • Chemoreceptors
  • Electromagnetic receptors
  • Thermoreceptors
  • Pain receptors
• Mechanoreceptors


  • Sense physical deformation caused by stimuli like pressure, stretch, motion, and sound
• Chemoreceptors


  • Transmit information about total solute concentration or respond to individual molecules
• Electromagnetic receptors


  • Detect electromagnetic energy like light, electricity, and magnetism
• Thermoreceptors


  • Respond to heat or cold and help regulate body temperature
• Pain receptors (nociceptors)


  • Detect stimuli reflecting harmful conditions like excess heat, pressure, or chemicals
• Hearing and equilibrium are related senses that detect moving fluid or settling particles using mechanoreceptors
• Hearing


  1. Vibrating objects create pressure waves

  2. Pressure waves cause basilar membrane to vibrate

  3. Bending of hair cells depolarizes membranes

  4. Action potentials sent to brain via auditory nerve
• Utricle and saccule


  • Contain otoliths that allow perception of position relative to gravity or linear movement
• Semicircular canals


  • Detect rotational movement and head position
• Sound transmission through the vestibular canal

  1. Pressure waves in the canal cause the basilar membrane to vibrate

  2. Bending of hair cells depolarizes the membranes of mechanoreceptors

  3. Sends action potentials to the brain via the auditory nerve
• Hair cell response to bending

  • No bending: less neurotransmitter released
  • Bending in one direction: more neurotransmitter released
  • Bending in other direction: less neurotransmitter released
• Organs of the inner ear that detect body movement, position, and balance

  • Utricle
  • Saccule
  • Three semicircular canals
• Otoliths


  Granules in the utricle and saccule that allow us to perceive position relative to gravity or linear movement
• The eye detects color and light, but the brain assembles the information and perceives the image
• In terrestrial animals, gustation (taste) is dependent on the detection of chemicals called tastants, and olfaction (smell) is dependent on the detection of odorant molecules
• In aquatic animals there is no distinction between taste and smell
• Taste receptors of insects are in sensory hairs located on feet and in mouth parts
• Five taste perceptions in humans and other mammals

  • Sweet
  • Sour
  • Salty
  • Bitter
  • Umami
• Researchers believe that an individual taste cell expresses one receptor type and detects one of the five tastes
• Taste buds


  Receptor cells for taste in mammals, modified epithelial cells organized into taste buds, located in several areas of the tongue and mouth
• Most taste buds are associated with projections called papillae